There has been known a deficiency inspecting device for a sheet-shaped product including an optical film (Patent Literature 1). The deficiency inspecting device receives information on a deficiency from a protective film inspecting section, and forms a data code (for example, a two-dimensional code or a QR Code [registered trademark]) having a fixed pitch and indicative of the deficiency. The deficiency inspecting device forms such a data code on a surface at an end of a PVA film original sheet together with information on the position and production identification.
With the above arrangement, obtaining information on the position of a deficiency in a sheet-shaped product makes it possible to specify which film has the deficiency among a plurality of films prepared by cutting the sheet-shaped product lengthwise in a slitting step. Subsequently carrying out an appropriate measure for any deficient film, for example, cutting off a deficient portion, allows for production of a film having no deficiency.